The present invention relates to an information processing apparatus having an address extension function, and more particularly to an information processing apparatus capable of extending an address space while keeping compatibility with already developed softwares.
In a current general purpose computer architecture, an instruction counter, general registers and the like all of 31 bits or 32 bits are generally used. Softwares have been developed also on the basis of 31 bit address. A general purpose computer architecture of this type is discussed, for example, in IBM System 370 Extended Architecture Principles of Operation, SA22-7085-1, 1987, pp 3-21 to 3-38.
Data amount to be processed has increased nowadays, and both virtual and real addresses of 31 bits or more have become necessary. In configuring a new architecture with 31 or more bit addresses, it is important to keep compatibility with those architectures with 31 bit addresses already developed. Namely, it is necessary for an information processing apparatus of a new architecture to be capable of using softwares with 31 bit addresses without any modification.